OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

January 31, 1992

Mr. Mark A. Hatch
Data Instruments, Inc.
100 Discovery Way
Acton, Massachusetts 07210

Dear Mr. Hatch:

Thank you for your December 3, 1991 letter of inquiry on the applicability of Occupational Safety and Health Administration (OSHA) standards at 29 CFR 1910.217 on specialized devices used to control mechanical power presses. These specialized devices use either optical or capacitive, that is, radio frequency (RF), sensing fields. In your letter you indicate that these specialized devices are intended to provide two-hand controls, which may reduce the risk of cumulative trauma disorders to employees operating mechanical power presses. Also, you ask whether OSHA would consider that these special control devices "are in fact presence sensing devices and that using them without additional safeguards would constitute presence sensing device initiation (PSDI)."

The use of two-hand controls with improved ergonomic characteristics is encouraged by OSHA. Note that a device intended for use within the control system of a mechanical power press must comply with the control reliability requirements of 29 CFR 1910.217(b)(13) unless operating the control system has no effect on the protection of employees against point of operation injuries.

The employer is required to provide point of operation devices on workplace mechanical power presses to protect operator employees by one of the alternative means required by 29 CFR 1910.217(c)(3). By 29 CFR 1910.217(c)(3)(iii), a presence sensing point of operation device shall protect the operator when the employer, in compliance with 29 CFR 1910.217(c)(3)(i)(a), opts to prevent or stop the normal stroking of the press if the operator's hands are placed inadvertently in the point of operation. Presence sensing point of operation devices must comply with the requirements at 29 CFR 1910.217(c)(3)(iii) and specifically 29 CFR 1910.217(c)(3)(iii)(b). By this latter standard, presence sensing point of operation devices may not be used as a tripping means to initiate slide motion, except when used in total conformance with the PSDI requirements at 29 CFR 1910.217(h).

Compliance with OSHA standards at 29 CFR 1910.217 is determined by evaluating the installation and operation of mechanical power presses and their particular controls and safeguards to protect employees from injury in the workplace. Therefore, we cannot make a judgment on whether, in anticipated circumstances, your devices as intended to be used in the workplace would meet OSHA requirements to provide for workers safety and health.

We appreciate your interest in employee safety and health. If we may be of further assistance, please do not hesitate to contact us.


Patricia K. Clark, Director
Directorate of Compliance Programs